Hybrid hydraulic systems for vehicles harness the lost kinetic energy that occurs during braking of a vehicle. Kinetic energy is captured by a power transfer system, and subsequently stored as potential energy in an accumulator. This potential energy is later transferred very quickly to kinetic energy which used to accelerate the vehicle, thereby improving fuel efficiency. The accumulator systems store a large amount of energy. Typical accumulator systems include a separate accumulator tank and a separate reservoir tank. Unfortunately, this configuration of accumulator and reservoir tanks presents problems.
Because of the large amount of potential energy stored in the accumulator systems, such systems must be designed to avoid uncontrolled release of the potential energy. One approach has been to make the walls of the accumulators thick enough that catastrophic failure becomes virtually impossible. Unfortunately, this increases the mass of the accumulator system and can negate any energy savings from the energy recovery since the acceleration of the vehicle must also accelerate the massive accumulator. The separate accumulator and reservoir tank configuration also presents a problem, because the separate tanks require more space on the chassis of the vehicle, thus decreasing available room for passengers, cargo, or other components.
It would be desirable to have an integral accumulator/reservoir system that would overcome the above disadvantages.